Can a stun gun?

If they are positioned in such a way to complete an electrical circuit - yes.

During basic law enforcement taser school, several students link their arms and electrodes are placed on the arm of the students on either end. All of the students in the line are zapped.

The same concept works for getting shocked with an external defibrillator - which is why the paramedic or doctor needs to make certain noone is touching the patient before shocking him.

Yes. The LAPD SWAT team had 30 people hold hands during a training class and hooked the TASER to the people on the ends. All 30 got hit at once.

Ouch.

It can happen, but it seems to me that the two people would have to be positioned in an unlikely manner. I would pick a different plot line if I were you. How about both of them getting hit with a baton? That makes more sense, but it might not have the effect you're looking for. Good night!

An electrical charge travels so yes if they were holding hand and one got tazored the other person would feel it too. Watch Jackass 2 they test this theory but I believe with a car battery.

Yes becsue you create a circiut, just like an electrical circuit in the wiring in your house. But, the circuit created by humans, not all of them would feel the same intesity of shock, the first one would feel it the most and the the next person less and the next person less and so on and so on.

ok, lets say one person got hit my the positive lead, and the other by the negative lead, while both people holding hands, would be possible. ive tried it with a tazer, and it worked!

Yep, I saw it happen on TV in Denver the other night. They tazered this guy and the cop next to him got tazered too. Pretty cool.

well ur story is fictional so anything can happen and it probably won't work unless there is water between the two

No, don't believe so.